The invention relates to a method and apparatus for cleaning and inspecting underground pipes and conduits in order to facilitate repair and replacement of such under ground pipes.
A known technique for replacing sanitary sewer lines and various other underground conduits and pipes is to burst or expand the existing pipe and then pull a replacement pipe through the expanded bore. In one variation of this process, a horizontal directional drill advances a drill string with pipe bursting or splitting tool affixed to the end of the drill string. The system may include a impact device mounted at the end of the drill string such as a rotary impactor (see U.S. Pat. No. 5,782,311) or a pneumatic impact tool that delivers cyclic impacts to the bursting or splitting tool. The replacement pipe is attached to the bursting or splitting tool and pulled through the bore behind it.
It is common practice to clean an existing sanitary sewer pipe prior to a line replacement operation. Lateral connections, for example to residences, must be accurately located and marked to avoid excessive excavation. However, in many cases, existing underground pipelines will have an accumulated buildup of solids, grease, and wax-like materials that may interfere with the inspection, bursting, splitting and/or replacement operations. The accumulated buildup may also prevent or interfere with locating pipe joints, which in the case of cast iron pipes may require particular attention during the splitting operation.
In the past, sanitary sewers have been cleaned with specialized equipment including high pressure water jets operating at 2000 psi. This method of cleaning requires the use of a jet truck, i.e., a truck specially equipped with one or more specialized pumps designed to deliver moderate volumes of water at extremely high pressures, a high pressure hose to reach the area or areas to be cleaned, and nozzles specially designed to direct the high pressure water into a jet capable of cutting the materials. The nozzles are radially spaced and angled rearwardly so that the discharge of water through the nozzles creates a reaction force to propel the high pressure hose through the pipe being cleaned. A xe2x80x9csoupxe2x80x9d of suspended solids, grease and water flows downstream through the pipeline. In some cases the jet truck will vacuum this soup from a manhole, the same manhole the spray head was introduced from.
This invention makes opportunistic use of the presence of a horizontal drilling machine using a rigid drill string during a pipe bursting and replacement operation. Conventionally, horizontal directional boring machines are used only for the pipe bursting and replacement stage of the operation. The present invention provides accessories by which other useful steps can be carried out using the directional boring machine, including cleaning and inspecting existing pipes.
The invention provides a method of replacing an existing underground pipe, especially a sanitary sewer line, using a boring machine that advances a drill string of hollow rods through the existing pipe. Such a method includes the steps of:
(a) mounting a rotary cleaning tool on a distal end of the drill string;
(b) moving the cleaning tool progressively through the underground pipe while rotating the drill string in order to clean the inside of the pipe;
(c) flushing debris loosened by the cleaning tool from the pipe using a pressure fluid;
(d) removing the cleaning tool from the drill string and mounting a camera assembly on the distal end of the drill string;
(e) moving the camera and drill string through the underground pipe on the drill string and inspecting the inside surface of the pipe with the camera;
(f) removing the camera from the drill string and replacing it with a pipe destroying apparatus;
(g) moving the pipe destroying apparatus through the pipe to destroy the existing pipe; and
(h) installing a replacement pipe along the same line as the destroyed existing pipe. The existing pipe can be destroyed by any known method appropriate to the material the pipe is made from, such as pipe bursting or pipe slitting and spreading. According to preferred forms of the invention, the pressure fluid is supplied through the drill string and ejected from the cleaning tool as the cleaning tool advances through the existing pipe.
The existing pipe is typically a sanitary sewer line having a number of lateral line connections. As such, step (e) preferably involves determining the locations of the lateral line connections to the existing pipe, such as by connecting a sonde to the camera and marking the position of the lateral above ground by detecting the sonde""s position when the camera shows a lateral connection. For this purpose, the camera is typically a video camera that provides a live feed of the pipe interior and has a built in light source.
According to a preferred form of the invention, steps (a) to (c) are performed as the drill string is extended from an entrance to an exit at opposite ends of the existing pipe. The entrance and exit may be openings in a pit or manhole. Step (d) is then performed while the distal end of the drill string is near the exit, and step (e) is performed as the drill string is retracted from the exit back to the entrance. In this manner the existing pipe is cleaned, flushed and then inspected in one down and back cycle of the drilling machine. The same drilling machine is then used for the subsequent steps of destroying the existing pipe, replacing it with a new pipe, and optionally de-beading the new pipe after lateral connections have been welded on.
The pipe inspection and cleaning aspects of the invention can also be used separately when the occasion requires and specialized equipment is not available. A method for inspecting an inside surface of a pipe using a horizontal boring machine that advances a drill string of hollow rods through the pipe includes the steps of attaching a camera to a distal end of the drill string, moving the camera through the underground pipe on the drill string, and imaging the inside surface of the pipe with the camera while the camera is inside the pipe. A method of cleaning an underground pipe includes the steps of mounting a rotary cleaning tool on a distal end of the drill string, moving the cleaning tool progressively through the underground pipe while rotating the drill string in order to clean the inside of the pipe, and flushing debris loosened by the cleaning tool from the pipe using a pressure fluid.
The invention further provides a pipe cleaning tool useful in such a method adapted to be mounted on the end of a drill string and advanced through an underground pipe with a horizontal drilling machine to clean the pipe. Such a tool includes a generally cylindrical body including a front nose section, a plurality of side flats at intervals around the circumference of the body, and a rear connecting portion configured for connecting the pipe cleaning tool to the drill string. A flexible flap mounted on each of the flats extends tangentially from the body and is configured to scrape along the inside of the pipe as the cleaning tool is advanced through the pipe. The body further includes fluid passages for communicating through the drill string with a source of a pressure fluid, and a plurality of nozzles connected to the fluid passages for ejecting the pressurized fluid in a radial direction as the tool is advanced through the pipe.
The invention also provides an apparatus for inspecting a pipe. Such a device includes an electronic camera and an elongated carrier body having a recess adapted to receive the camera therein, an end connecting portion configured for mounting the carrier body on a drill string, and an opening whereby the camera can be positioned to capture an image through the opening. The camera is preferably a video camera and transmits its signal through a cable to a video display above, permitting the operator to inspect the condition of the line interior and locate lateral branch lines. These and other aspects of the invention are described in the detailed description that follows.